MC68332ACEH20 Datasheet, PDF (33/88 Pages) Freescale Semiconductor, Inc – 32-Bit Modular Microcontroller

Freescale Semiconductor, Inc.
3.5.3 Base Address Registers
A base address is the starting address for the block enabled by a given chip select. Block size deter-
mines the extent of the block above the base address. Each chip select has an associated base register
so that an efficient address map can be constructed for each application. If a chip-select base address
register is programmed with the same address as a microcontroller module or memory array, an access
to that address goes to the module or array and the chip-select signal is not asserted.
CSBARBT — Chip-Select Base Address Register Boot ROM
$YFFA48
15
14
13
12
11
10
9
8
7
6
5
4
3
2
0
ADDR ADDR ADDR ADDR ADDR ADDR ADDR ADDR ADDR ADDR ADDR ADDR ADDR
23
22
21
20
19
18
17
16
15
14
13
12
11
BLKSZ
RESET:
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
CSBAR[10:0] —Chip-Select Base Address Registers
$YFFA4C–$YFFA74
15
14
13
12
11
10
9
8
7
6
5
4
3
2
0
ADDR ADDR ADDR ADDR ADDR ADDR ADDR ADDR ADDR ADDR ADDR ADDR ADDR
23
22
21
20
19
18
17
16
15
14
13
12
11
BLKSZ
RESET:
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
ADDR[23:11] — Base Address Field
This field sets the starting address of a particular address space. The address compare logic uses only
the most significant bits to match an address within a block. The value of the base address must be a
multiple of block size. Base address register diagrams show how base register bits correspond to ad-
dress lines.
BLKSZ — Block Size Field
This field determines the size of the block that must be enabled by the chip select. The following table
shows bit encoding for the base address registers block size field.
Block Size Field
000
001
010
011
100
101
110
111
Block Size
2K
8K
16 K
64 K
128 K
256 K
512 K
1M
Address Lines Compared
ADDR[23:11]
ADDR[23:13]
ADDR[23:14]
ADDR[23:16]
ADDR[23:17]
ADDR[23:18]
ADDR[23:19]
ADDR[23:20]
3.5.4 Option Registers
The option registers contain eight fields that determine timing of and conditions for assertion of chip-
select signals. For a chip-select signal to be asserted, all bits in the base address register must match
the corresponding internal upper address lines, and all conditions specified in the option register must
be satisfied. These conditions also apply to providing DSACK or autovector support.
MC68332
MC68332TS/D
For More Information On This Product,
Go to: www.freescale.com
MOTOROLA
33